From Rabbi Aryeh Kaplan, The Light Beyond: Adventures in Hassidic Thought (Moznaim), pp. 213-214. Footnotes have been omitted from this online version.
Self-Nullification Through Prayer
Maggid of Mezeritch
Think of yourself as nothing, and totally forget yourself when you pray. Only have in mind that you are praying for the Divine Presence.
You can then enter the Universe of Thought, a state that is beyond time. Everything in this realm is the same, life and death, land and sea . . . But in order to enter the Universe of Thought where all is the same, you must relinquish your ego, and forget all your troubles.
You can not reach this level if you attach yourself to physical, worldly things. You are then attached to the division between good and evil, which is included in the seven days of creation. How then can you approach a level above time, where absolute unity reigns.
Furthermore, if you consider yourself as "something," and ask for your own needs, God cannot clothe Himself in you. God is infinite, and no vessel can hold Him at all, except when a person makes himself like Nothing (Maggid Devarav LeYaakov, 159).
In prayer, you must place all your strength in the words, going from letter to letter until you completely forget your body. Thinking how the letters permute and combine with each other, you will have great delight.
If this is a great physical delight, it is certainly a spiritual delight. This is the Universe of Formation (Yetzirah), [the world of speech]. The letters then enter your thoughts, and you do not even hear the words you speak. This is the Universe of Creation (Beriyah) [the world of thought]. You then come to the level of Nothingness, where all your [senses and] physical powers are nullified. This is the Universe of Nearness (Atziluth), the Attribute of Wisdom (Maggid Devarav LeYaakov, 97).